Palladium-mediated substitution of the closo-B12H12(-2) and nido-7,8-C2B9H12(-1) ions by PMe2Ph: The single-crystal structure studies of 1,7-(PMe2Ph)2-closo-B12H10 and 9-PMe2Ph-nido-7,8-C2B9H11

Article abstract of DOI:10.1016/j.poly.2007.04.025

Treatment of Na₂[closo-B₁₂H₁₂] with one mole equivalent of (PMe₂Ph)₂PdCl₂ in THF at room temperature formed Na[closo-(PMe₂Ph)-B₁₂H₁₁], 1,7- and 1,12-(PMe₂Ph)₂-closo-B₁₂H₁₀ in moderate yield. Reaction of K[nido-7,8-C₂B₉H₁₂] with one half a mole equivalent of (PMe₂Ph)₂PdCl₂ in CH₂Cl₂ at room temperature formed a mixture of 9-PMe₂Ph-nido-7,8-C₂B₉H₁₁ and 10-PMe₂Ph-nido-7,8-C₂B₉H₁₁ in overall good yield. Single-crystal X-ray structures of 1,7-(PMe₂Ph)₂-closo-B₁₂H₁₀ and 9-PMe₂Ph-nido-7,8-C₂B₉H₁₁ are reported.

Full text of DOI:10.1016/j.poly.2007.04.025

Polyhedron 26 (2007) 3793–3798
www.elsevier.com/locate/poly
Palladium-mediated substitution of the closo-B12H12(ꢀ2)
and nido-7,8-C2B9H12(ꢀ1) ions by PMe2Ph: The single-crystal
structure studies of 1,7-(PMe2Ph)2-closo-B12H10
and 9-PMe2Ph-nido-7,8-C2B9H11
a
a
a
b,
*
Steve A. Jasper Jr. , John Mattern , John C. Huffman , Lee J. Todd
a
Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN 47405-7201, USA
b
Gosport Scientific LLC, 9608 W. Hedrick Rd., Gosport, IN 47433-9507, USA
Received 6 February 2007; accepted 6 April 2007
Available online 1 May 2007
Abstract
Treatment of Na2[closo-B12H12] with one mole equivalent of (PMe2Ph)2PdCl2 in THF at room temperature formed Na[closo-
(PMe2Ph)-B12H11], 1,7- and 1,12-(PMe2Ph)2-closo-B12H10 in moderate yield. Reaction of K[nido-7,8-C2B9H12] with one half a mole
equivalent of (PMe2Ph)2PdCl2 in CH2Cl2 at room temperature formed a mixture of 9-PMe2Ph-nido-7,8-C2B9H11 and 10-PMe2Ph-
nido-7,8-C2B9H11 in overall good yield. Single-crystal X-ray structures of 1,7-(PMe2Ph)2-closo-B12H10 and 9-PMe2Ph-nido-7,8-
C2B9H11 are reported.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Keywords: Phosphine-substituted carborane; Palladium-mediated substitution; Polyhedral borane; Boron
1. Introduction
This type of reaction suggests the possibility that easily-
accessible palladium(II) coordination compounds may be
The use of palladium(II) reagents in synthetic organic used to activate a B–H bond of a polyhedral borane or het-
chemistry is widespread, and a large variety of transforma- eroatom borane and substitute a ligand there, as repre-
tions may be accomplished [1]. The Suzuki reaction, the sented in the general case of:
palladium catalyzed coupling of an organoboron reagent
with aryl- or alkenylhalides, is a very powerful method
for carbon–carbon bond formation [2].
nꢀ
L2PdCl2 þ ½ðcageÞB ꢀ Hꢁ
! ½ðcageÞB ꢀ Lꢁðnꢀ1Þꢀ\LnPdXm"
ð1Þ
The B-alkyl Suzuki–Miyaura cross-coupling reaction
extends this process to involve an sp3 carbon in the coupling
event [3]. The B-arylation of p-carborane was accomplished
by palladium-catalyzed cross-coupling of an arylboronic
acid and 2-I-p-carborane [4]. Palladium-catalyzed borane–
olefin or carborane–olefin coupling reactions were reported
by Sneddon and coworkers [5]. In these cases, a B–H bond
must be ‘‘activated’’ so that substitution may take place.
In this type of reaction, a neutral 2-electron donor ligand
(:L) transfers from palladium to a polyhedral borane anion
site, substituting for a hydride ion resulting in a ‘‘charge-
compensated’’ borane species. There are also as yet unchar-
acterized palladium byproduct(s) represented by ‘‘LnPdXm’’
species in Eq. (1).
Numerous charge-compensated polyhedral boranes and
carboranes were described over 40 years ago [6,7]. These
included phosphine-substituted B12H12(ꢀ2) derivatives [6].
Reaction of PMe3 with diborane-6 in a stainless steel vessel
at 175 ꢁC for 10 h formed [H2B(PMe3)2][PMe3-B12H11] and
*
Corresponding author. Tel.: +1 812 876 5195.
E-mail address: toddlj@indiana.edu (L.J. Todd).
0277-5387/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2007.04.025

3794
S.A. Jasper Jr. et al. / Polyhedron 26 (2007) 3793–3798
a small amount of (PMe3)2B12H10 [6]. These compounds equipped with a magnetic stir bar and dissolved in 40 mL
were characterized by elemental analysis only. The possibil- dry THF. In a separate flask, (PMe2Ph)2PdCl2 (4.35 g,
ity of isomers of (PMe3)2B12H10 was not addressed.
9.6 mmol) was dissolved in 240 mL of dry THF and then
During our studies of the syntheses of pallada-diarsabor- transferred slowly via cannula to the stirred solution of
anes, we obtained some products having charge-compensat- Na2B12H12. The mixture was stirred at room temperature
ing Lewis base ligands bonded to cage boron atoms [8]. for 1 day during which time the color changed from orange
Many other transition metal-mediated substitution reac- to brown. The mixture was vacuum filtered to remove solid
tions of phosphines (PR3) onto boron atoms of polyhedral material. To the clear THF solution was added an excess of
cage molecules have been reported. For example, reaction NaBH4 to reduce all remaining palladium species to Pd0.
of PdI2(PPh3)2 with Cs[TeB10H11] in refluxing toluene Vigorous gas evolution occurred as the mixture was
formed 2-I-2-PPh3-closo-2,1-PdTeB10H9(PPh3) in good brought to reflux, which was continued for 6 h. The mixture
yield [9]. Another example is the conversion of 8,8- was left at room temperature over night to complete the
(PMe2Ph)2-nido-8,7-PtCB9H11 in refluxing toluene to 6- reduction. The mixture was filtered through a coarse-fritted
PMe2Ph-closo-1-CB9H8 in good yield [10]. These results filter under nitrogen to remove the reduced metal solids
lead us to study more generally some palladium-assisted (Caution: The filtered solids may spontaneously ignite if
substitution reactions of B10H10(ꢀ2) and B12H12(ꢀ2) ions, exposed to air). The THF was removed from the filtrate
including a brief mention of 1,7-(PMe2Ph)2B12H10 [11]. by rotary evaporation leaving a thick white oil. This crude
Recently, the synthesis and crystal structure determination mixture was dissolved in CH2Cl2 and mixed with 3 g of sil-
˚
of N(n-Bu)4[PPh3-B12H11] was reported [12]. This derivative ica gel (Merck grade 60, 230–400 mesh, 60 A). The CH2Cl2
was prepared by reaction of [N(n-Bu)4]2[B12H11I] with was removed in vacuo and the solids were packed on a
Pd(Ph3)4.
35 cm · 2.4 cm silica gel chromatography column, and
In this report, we describe in detail the reaction of eluted initially with 1:1 (v/v) toluene:CH2Cl2. There were
(PMe2Ph)2PdCl2 with Na2[B12H12] and also with K[7,8- four bands. Band I, Rf = 0.96 by TLC (CH2Cl2 mobile
C2B9H12] to give several charge-compensated products in phase, I2 development) was determined by 11B NMR to
moderate yields.
be (PMe2Ph)BH3, 11B{1H}, ꢀ38 ppm, JB–P = 61 Hz [15]
Band II, Rf = 0.85 was a white solid (353 mg, 8.82% yield)
and Rf = 0.6 was determined to be 1,12-(PMe2Ph)2-B12H10
by 11B NMR (see Table 1). Band III, 1,7-(PMe2Ph)2-
B12H10, a white solid, m.p. 202–206 ꢁC (1.201 g, 30.14%
yield). And band IV was eluted with 1:1 CH2Cl2:CH3CN
2. Experimental
2.1. Physical measurements
Boron (11B) NMR spectra were obtained at 115.85 MHz and was found to be a relatively insoluble compound,
(21 ꢁC) with a Nicolet NT-360 spectrometer and were exter- whose 11B NMR spectrum was consistent with Na-
nally referenced to BF3(OEt2). Phosphorus (31P) NMR [(PMe2Ph)-B12H11] (see Table 2–6).
spectra were obtained at 146.2 MHz (21 ꢁC) and externally
referenced to 85% H3PO4. Proton (1H) NMR spectra were 2.4. PMe2Ph-nido-7,8-C2B9H11 isomers
obtained at 361.1 MHz (21 ꢁC) and internally referenced to
trace protonated solvent. In all NMR spectra, positive
In a two-neck, round-bottom flask equipped with a sep-
chemical shifts were downfield. Melting points were tum and nitrogen inlet were placed K[nido-7,8-C2B9H12]
obtained in sealed, evacuated capillaries and are (172 mg, 0.998 mmol) and (PMe2Ph2PdCl2 (226 mg,
uncorrected.
0.498 mmol), and 25 mL dry distilled CH2Cl2. The dicar-
bollide salt did not fully dissolve. The solution gradually
darkened from yellow to orange to brown while stirring
overnight. The reaction mixture was filtered on a coarse-
2.2. Materials
All reactions were performed under an atmosphere of pre- fritted funnel, to leave behind some gray solids. The brown
purified nitrogen. Tetrahydrofuran (THF) was freshly dis- filtrate was rotary evaporated, and the remaining solids
tilled from sodium benzophenone ketyl. Dichloromethane extracted with benzene. An excess of NaBH4 was added
(CH2Cl2) was distilled from P2O5. Potassium dodecahydro- to the benzene solution to reduce all remaining palladium
7,8-dicarba-nido-undecaborate(1ꢀ), K[7,8-C2B9H12], was species to Pd0. The solution was brought to reflux for 4 h.
prepared by a literature method [13]. Bis(dimethylphenyl- The mixture was filtered through a coarse-fritted funnel
phosphine) palladium(II) chloride was prepared by the to remove fluffy grayish solids, resulting in a nearly color-
method of Wild et al. [14].
less filtrate. The benzene was rotary evaporated to a yellow
oil (221 mg, 81.9% crude yield). 11B NMR indicated that
the oil consisted of a mixture of 9-PMe2Ph-nido-7,8-
C2B9H11 (major product) and 10-PMe2Ph-nido-7,8-
C2B9H11 (minor product). Subsequent crystallization from
2.3. (PMe2Ph)2-closo-B12H10 isomers and Na[(PMe2Ph)-
closo-B12H11]
In a typical reaction scheme, Na2B12H12 (1.81 g, CH2Cl2/pentane at 5 ꢁC yielded pale yellow needles of 9-
9.6 mmol) was placed in a 500 mL round-bottom flask PMe2Ph-nido-7,8-C2B9H11.

S.A. Jasper Jr. et al. / Polyhedron 26 (2007) 3793–3798
3795
Table 1
11B NMR data
Table 3
31P{1H} NMR data
Compound
Chemical shift (ppm), (relative intensities)
[J (Hz)]
Compound
Chemical shift (ppm), multiplicity, JB–P (Hz)
ꢀ8.9, 1:1:1:1 quartet, 150
ꢀ7.8, 1:1:1:1 quartet, 151
11B–H
1,7-(PMe2Ph)2-B12H10
9-PMe2Ph-7,8-C2B9H11
1,12-(PMe2Ph)2-B12H10
1,7-(PMe2Ph)2-B12H10
ꢀ13.8, (10B) [129];
ꢀ16.1, (2B) [J
ffi 230 Hz]
11B–31P
ꢀ11.9, (4B); ꢀ13.6, (4B) [159];
ꢀ15.3, (2B); ꢀ16.2, (2B) [J
ffi 150 Hz]
11B–31P
Table 4
Crystallographic data
Na[(PMe2Ph)-B12H11
]
ꢀ11.1, (1B) [132]; ꢀ13.4, (5B) [138];
ꢀ14.9, (5B) [141]
Compound
1,7-(PMe2Ph)-
B12H10
9-PMe2Ph-7,8-
C2B9H11
11B–31P
ꢀ17.6, (1B) [J
¼ 141 Hz]
a
N(n-Bu)4[PPh3-B12H11
]
ꢀ8.4, (1B); ꢀ12.3 (5B); ꢀ13.5, (5B); ꢀ17.9 (1B)
Molecular weight
Crystal system, Z
Unit cell
416.10
triclinic, P1, 2
270.55
monoclinic, C2/c, 8
ꢀ
[J
¼ 134 Hz]
11B–31P
˚
9-PMe2Ph-7,8-C2B9H11
ꢀ4.1 (1B), [138]; ꢀ10.1 (1B), [145];
A (A)
9.607(1)
14.997(2)
8.934(1)
99.32(0)
109.86(0)
88.05(0)
1194.31
1.157
0.71069
1.799
22.5
23.5
2.0
29.978(9)
6.769(2)
17.063(5)
˚
ꢀ15.6 (1B), [J
¼ 155 Hz]; ꢀ16.1 (1B);
11B–31P
B (A)
˚
ꢀ18.0 (1B); ꢀ23.6 (1B) [156]; ꢀ25.5 (1B) [145]
C (A)
ꢀ28.3 (1B) [129]; ꢀ36.2 (1B) [143]
a (ꢁ)
b (ꢁ)
c (ꢁ)
115.02(1)
10-PMe2Ph-7,8-C2B9H11 ꢀ11.0 (2B); ꢀ15.0 (1B); ꢀ16.1 (2B);
ꢀ20.7 (2B) [154]; ꢀ34.5 (1B)
3
˚
V (A )
3137.44
1.146
0.71069
1.481
22.5
23.5
2.0
0.25
[J
ffi 145 Hz]
11B–31P
qcalc (g cmꢀ3
)
ꢀ36.1 (1B)
˚
k (A)
9-PPh3-7,8-C2B9H1b1
9-PPh3-7,8-C2B9H1c1
ꢀ2.97 (1B); ꢀ9.26 (1B); ꢀ14.89 (1B)
l (cmꢀ1
)
[J
¼ 155 Hz]; ꢀ16.37 (1B)
11B–31P
Det-samp distance (cm)
Samp-source distance (cm)
Takeoff angle (ꢁ)
Average x scan width at
half-height (ꢁ)
Scan speed (ꢁ/min)
Scan width (ꢁ)
Single bkgd time at
extremes of scan (s)
Aperture size (mm)
Collection limit (2h, ꢁ)
Total number of reflections
Number of unique intensity
Number with F > 0.0
Number with F > 2.33*r(F)
R for averaging
Final residuals
R(F)
Rw(F)
Goodness-of-fit for last cycle
Maximum D/r for last cycle
ꢀ17.80 (1B); ꢀ23.46 (1B), ꢀ25.50 (1B)
ꢀ26.89 (1B); ꢀ36.04 (1B)
0.25
ꢀ1.42 (1B); ꢀ7.76 (1B); ꢀ12.98 (1B)
[J
¼ 149 Hz]
11B–31P
4.0
10.0
1.8 + dispersion
4
ꢀ14.58 (1B); ꢀ16.20 (1B); ꢀ21.86 (1B)
2.0 + dispersion
4
ꢀ23.78 (1B); ꢀ25.33 (1B); ꢀ34.47 (1B)
10-PPh3-7,8-C2B9H1c1
ꢀ9.86 (2B); 14.16 (3B); ꢀ19.02 (2B)
ꢀ32.18 (1B) [J
¼ 150 Hz]; ꢀ35.83 (1B)
3.0 · 4.0
6–45
3384
3133
3018
3.0 · 4.0
6–45
2296
2059
1927
11B–31P
9-PPh2Me-7,8-C2B9H1c1
ꢀ2.34 (1B); ꢀ8.56 (1B); ꢀ12.61 (1B)
11B–31P
[J
¼ 164 Hz]
ꢀ15.12 (1B); ꢀ16.60 (1B); ꢀ22.13 (1B);
ꢀ23.90 (2B);
2714
0.011
1626
0.032
ꢀ26.52 (1B); ꢀ35.04 (1B)
10-PPh2Me-7,8-C2B9Hc11 ꢀ9.72 (2B); ꢀ14.50 (3B); ꢀ19.25 (2B)
0.0338
0.0366
1.938
0.05
0.0403
0.0425
1.334
0.11
ꢀ33.02 (1B) [J
¼ 150 Hz]; ꢀ36.05 (1B)
11B–31P
a
b
c
Ref. [12], CHCl3 solvent.
Ref. [22], solvent, CH2Cl2.
Refs. [20,21].
Det-samp dist, detector to sample distance; Samp-source distance, sample
to X-ray source distance; Single bkgd time at extremes of scan, single
background time at extremes of scan.
Table 2
1H NMR data
2.5. Crystal structure determinations – general
Compound
Chemical shift (ppm), (relative intensities)
assignt, multiplicity, JH–P (Hz)
The diffractometer utilized for data collection was
designed and constructed locally. The apparatus comprised
a Picker X-ray generator and Picker four-circle goniostat
equipped with a Furnas Monochromater (HOG crystal)
was modified by addition of stepping motors (Slo-Syn) on
each of the four axes, and a fifth motor drives a 20-position
filter/attenuator wheel. The latter allows top/bottom-left/
right alignment of reflections. All motors are driven by a
locally designed ISA board in an IBM-PC compatible com-
puter. The computer also has a timer/scaler board which is
used to accumulate the counts from the scintillation counter
2
1,7-(PMe2Ph)2-B12H1a0
1,12-(PMe2Ph)2-B12H10
9-PMe2Ph-7,8-C2B9H11
1.78, (12H), PMe2, doublet, 12.2
7.4–7.6, (10H), PPh, multiplet
1.56, (12H), PMe2, doublet, 10.3
7.4–7.6, (10H), PPh, multiplet
1.81, (3H), PMe2, doublet, 11.9
1.89, (3H), PMe2, doublet, 12.1
2.23 (2H), H-Carb.
7.58–7.77, (5H) PPh, multiplet
a
CDCl3 solvent.

3796
S.A. Jasper Jr. et al. / Polyhedron 26 (2007) 3793–3798
Table 5
2.7. Crystal structure determination of
9-(PMe2Ph)-7,8-C2B9H11
˚
Selected bond distances (A) for 1,7-(PMe2Ph)2-closo-B12H10
P(13)–B(1)
P(22)–B(7)
B(1)–B(2)
B(1)–B(3)
B(1)–B(4)
B(1)–B(5)
B(1)–B(6)
B(2)–B(3)
B(2)–B(6)
B(2)–B(7)
B(2)–B(11)
B(3)–B(4)
B(3)–B(7)
B(3)–B(8)
B(4)–B(5)
B(4)–B(8)
1.9055(25)
1.9113(25)
1.768(3)
1.760(3)
1.769(3)
1.765(4)
1.775(3)
1.804(3)
1.794(4)
1.769(3)
1.789(3)
1.789(3)
1.763(3)
1.791(4)
1.790(4)
1.773(4)
B(4)–B(9)
B(5)–B(6)
B(5)–B(9)
1.787(4)
1.792(4)
1.776(4)
1.785(4)
1.788(4)
1.780(4)
1.770(3)
1.778(3)
1.772(3)
1.787(4)
1.799(4)
1.802(4)
1.787(4)
1.783(4)
1.790(4)
1.795(4)
Pale yellow crystals of a 9-PPhMe2-7,8-C2B9H11 were
grown from a solution of CH2Cl2/pentane held at 5 ꢁC. A
small, well-formed fragment of a larger crystal was affixed
to the end of a glass fiber using silicone grease and trans-
ferred to the goniostat where it was cooled to ꢀ174 ꢁC
for characterization and data collection.
A systematic search of a limited hemisphere of reciprocal
space located a set of diffraction maxima with monoclinic
symmetry and systematic absences corresponding to one
of the centered space groups C2/c or Cc. Subsequent solu-
tion and refinement confirmed the centrosymmetric choice,
C2/c.
Data were collected using a continuous h, 2h scan tech-
nique with fixed backgrounds at each extreme of the scan.
Data were corrected for Lorentz and polarization effects.
The structure was solved by direct methods (MULTAN 78)
and standard Fourier techniques. All hydrogen atoms were
clearly visible in a difference Fourier phased on the non-
hydrogen atoms, and were included in the least squares
refinement.
B(5)–B(10)
B(6)–B(10)
B(6)–B(11)
B(7)–B(8)
B(7)–B(11)
B(7)–B(12)
B(8)–B(9)
B(8)–B(12)
B(9)–B(10)
B(9)–B(12)
B(10)–B(11)
B(10)–B(12)
B(11)–B(12)
Table 6
˚
Selected bond distances (A) for 9-(PMe2Ph)-nido-7,8-C2B9H11
P(12)–B(9)
B(1)–B(2)
B(1)–B(3)
B(1)–B(4)
B(1)–B(5)
B(1)–B(6)
B(2)–B(3)
B(2)–B(6)
B(2)–C(7)
B(2)–B(11)
B(3)–B(4)
B(3)–C(7)
B(10)–B(11)
1.905(3)
1.745(5)
1.774(5)
1.780(5)
1.781(4)
1.811(5)
1.760(5)
1.758(5)
1.694(4)
1.796(5)
1.779(4)
1.705(4)
1.870(5)
B(3)–C(8)
B(4)–B(5)
B(4)–C(8)
B(4)–B(9)
B(5)–B(6)
B(5)–B(9)
B(5)–B(10)
B(6)–B(10)
B(6)–B(11)
C(7)–C(8)
C(7)–B(11)
C(8)–B(9)
B(9)–B(10)
1.735(4)
1.762(5)
1.738(4)
1.761(4)
1.811(5)
1.752(5)
1.798(5)
1.800(5)
1.799(5)
1.534(4)
1.630(5)
1.589(5)
1.792(5)
A final difference Fourier was essentially featureless, the
3
˚
largest peak being 0.32 e/A . It was observed that this
peak was near the bridging hydride in the B9C2 cage,
and in fact would appear to bridge the two carbon atoms.
Attempts to model this as a partial occupancy bridging
hydrogen (with the occupancy of the located bridge
allowed to vary also) did not lead to a successful conver-
gence. In all probability, the hydrogen may ‘‘float’’ on the
face of the carborane, but the crystallographic evidence is
used with the goniostat. The control software, PCPS.EXE, lacking.
is the Picker software written by W. E. Streib of the Indiana
The structure is essentially the same as that reported for
University Molecular Structure Center (IUMSC). The 9-PPh3-nido-7,8-C2B9H11 [22] and 9-PMePh2-nido-7,8-
software for structure solution and refinement include C2B9H11 [20,21]. The diphenylmethyl phosphine structure
SHELXTL-PC and other versions of SHELX, as well as the XTEL
program library.
reported by Zakharkin et al. is remarkably similar, and is
nearly isostructural [20,21].
2.6. Crystal structure determination of
1,7-(PMe2Ph)2B12H10
3. Results and discussion
ꢀ2
3.1. PMe2Ph derivatives of the B12H12 ion
A typical crystal of 1,7-(PMe2Ph)2-B12H10 was grown by
slow evaporation from a 1:1 solution of toluene and CH2Cl2.
Reaction of Na2[B12H12] with (PMe2Ph)2PdCl2 at ambi-
The crystal was affixed to the end of a glass fiber using sili- ent temperature gave three phosphine-substituted products,
cone grease and transferred to the goniostat where it was each in low yield, namely Na[(PMe2Ph)B12H11], 1,7-
cooled to ꢀ174 ꢁC for characterization and data collection.
(PMe2Ph)2B12H10 (30% yield, approx.) and 1,12-
A systematic search of a limited hemisphere of reciprocal (PMe2Ph)2B12H10 (8% yield, approx.). The crude reaction
space located a set of diffraction maxima with no symmetry mixture was subsequently treated with excess sodium boro-
or systematic absences, corresponding to a triclinic space hydride to reduce all palladium-containing intermediates,
group. Subsequent solution and refinement of the structure ‘‘LnPdXm’’ to palladium metal. The first band to be eluted
ꢀ
confirmed the centrosymmetric choice, P1.
during column chromatography on silica gel, 1:1 (v/v) tol-
All hydrogen atoms were clearly visible in a difference uene:CH2Cl2 was (PMe2Ph)BH3 identified by 11B NMR,
Fourier phased on the nonhydrogen atoms, and were
d
¼ ꢀ38 ppm, JB–P = 61 Hz [15]. The boron in this com-
11B
refined isotropically in the final cycles of refinement. A final pound originated from NaBH4, added to the reaction mix-
difference Fourier was essentially featureless, the largest ture during workup and was not due to degradation of the
3
˚
peak being 0.34 e/A .
B12H12(ꢀ2) ion.

S.A. Jasper Jr. et al. / Polyhedron 26 (2007) 3793–3798
3797
Fig. 1. X-ray structure of 1,7-(PMe2Ph)2-closo-B12H10
.
The 1,12-(PMe2Ph)2B12H10 isomer was identified by its by Ph2PCl [20,21]. The 11B NMR spectra of 9- and 10-
11B NMR spectrum (see Table 1), which indicates a high PMe2Ph-nido-7,8-C2B9H11 agree with those of the two iso-
symmetry (D5h) and excludes the 1,2- or 1,7-isomer config- mers of the previously-reported (PPh3)-nido-7,8-C2B9H11
uration for this product.
[20–23] and (PMePh2)-nido-7,8-C2B9H11 [20,21] (see Table
An X-ray structural determination (Fig. 1) has been 1). The asymmetric 9-isomer has nine distinct resonances
undertaken on the other bis-phosphine isomer which was in its spectrum, whereas the Cs symmetric 10-isomer has
isolated and it conclusively proves it to be the 1,7-isomer.
six resonances in a 2:2:2:1:1:1 area ratio. In each of the 9-
The 1,7-(PMe2Ph)2B12H10 product was obtained in the isomer derivatives, the resonance at approximately ꢀ12.6
higher yield and is statistically the most favored bis-phos- to ꢀ15.6 ppm displayed 11B–31P spin–spin coupling of
phine derivative. Note that steric factors may be important 149–164 Hz. For the 10-isomer derivatives, the resonance
in this substitution process since to-date no 1,2-bis-phos- at ꢀ32.1 to ꢀ34.5 ppm displayed 11B–31P coupling of
phine product has been observed.
145–150 Hz.
The X-ray structure (Fig. 1) shows no anomalous dis-
˚
The X-ray structure (Fig. 2) shows no anomalous dis-
˚
tances or angles. The B–P distances, 1.9055 and 1.9113 A tances or angles. The B–P distance of 1.905 A is typical of
are quite usual, as are the B–B distances, which all are in
˚
the range 1.760–1.804 A. This compares favorably with
˚
the B–P distance of 1.928 A found for [N(n-Bu)4][(PPh3)-
B12H11] [12].
The B–P coupling constant for the 1,7-disubstituted prod-
uct as determined by 31P NMR was 150 Hz. This is within
the range of values observed for similar phosphine-borane
compounds (118–200 Hz) [16,17]. The value could not be
corroborated by 11B NMR, however, because the doublet
was not well-enough resolved for accurate measurement.
The B–P coupling constant observed for Na[(PMe2Ph)-
B12H11] in the 11B NMR spectrum was 141 Hz. This agreed
well with the B–P value reported previously for N(n-Bu)4-
[PPh3-B12H11] of 134 Hz [12].
3.2. PMe2Ph-nido-7,8-C2B9H11 isomers
Reaction of nido-7,8-C2B9H12(ꢀ1) ion with (PMe2Ph)2-
PdCl2 at ambient temperature yielded two isomers of
(PMe2Ph)-nido-7,8-C2B9H11. The combined crude yield of
both the asymmetric 9-isomer and symmetric 10-isomer
was 82%. The 11B NMR spectrum of the mixture suggested
that the 9-isomer predominated by approximately 2:1. Pref-
erence for reaction at the 9 position has been observed in
electrophilic substitution reaction of nido-7,8-C2B9H12(ꢀ1)
ion by I2 [18], by (C5H5)Fe(CO)2(alkene)(+1) ion [19] and
Fig. 2. X-ray structure of 9-(PMe2Ph)-nido-7,8-C2B9H11
.

3798
S.A. Jasper Jr. et al. / Polyhedron 26 (2007) 3793–3798
[7] W.H. Knoth, W.R. Hertler, E.L. Muetterties, Inorg. Chem. 4 (1965)
280.
[8] S.A. Jasper Jr., S. Roach, J.N. Stipp, J.C. Huffman, L.J. Todd, Inorg.
Chem. 32 (1993) 3072.
phosphine boranes; the B–B distances are all in the range
˚
1.745–1.870 A, and the B–C distances are slightly shorter
˚
at 1.589–1.738 A which is typical of carborane species.
[9] G. Ferguson, J.F. Gallagher, M. McGrath, J.P. Sheehan, T.R.
Spalding, J.D. Kennedy, J. Chem. Soc., Dalton Trans. (1993) 27.
[10] J.H. Jones, B. Stibr, J.D. Kennedy, M. Thornton-Pett, Coll. Czech.
Chem. Commun. 58 (1993) 2924.
[11] S.A. Jasper Jr., R.B. Jones, J. Mattern, J.C. Huffman, L.J. Todd,
Inorg. Chem. 33 (1994) 5620.
[12] R. Bernard, D. Cornu, D. Luneau, D. Naoufal, J.P. Scharff, P. Miele,
J. Organomet. Chem. 690 (2005) 2745.
[13] J. Plesek, S. Hermanek, B. Stibr, Inorg. Synth. 22 (1983) 231.
[14] N.K. Roberts, B.W. Skelton, A.H. White, S.B. Wild, J. Chem. Soc.,
Dalton Trans. (1982) 2093.
Appendix A. Supplementary material
CCDC 634413 and 634414 contain the supplementary
crystallographic data for this paper. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit@
ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.poly.2007.04.025.
[15] G.R. Eaton, W.N. Lipscomb, NMR Studies of Boron Hydrides and
Related Compounds, W.A. Benjamin, Inc., New York, 1969, p. 460.
[16] J. Bould, P. Brint, J.D. Kennedy, M. Thornton-Pett, J. Chem. Soc.,
Dalton Trans. (1993) 2335.
[17] G. Ferguson, J.F. Gallagher, J.P. Sheehan, T.R. Spalding, J.D.
Kennedy, R. Macias, J. Chem. Soc., Dalton Trans. (1993) 3147.
[18] F.P. Olsen, M.F. Hawthorne, Inorg. Chem. 4 (1965) 1839.
[19] F. Sato, T. Yamamoto, J.R. Wilkinson, L.J. Todd, J. Organomet.
Chem. 86 (1975) 243.
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